I. Field of the Invention
The present invention relates generally to a xe2x80x9csoft touchxe2x80x9d lifter for automotive Body in White geometry stations like framing stations.
II. Description of Related Art
In automotive Body in White geometry stations, automotive bodies in which the automotive body components have not been initially fixedly secured together, typically by welding, are supported on a skid. The skid, in turn, is moved by a conveyor system such as a roller table or belt conveyor along the conveyor line.
In order to form the final geometry and secure the automotive body components together, the skid together with the automotive body components supported by the skid is moved to a geometry station. Automotive tooling is provided at the geometry station, and a part of the tooling is initially positioned beneath the skid as the skid is moved into this geometry station. This underbody tooling typically includes a plurality of locators which register with receptors, such as locating holes, and N.C. blocks and clamps unit locating the outer surface of the body component.
The underbody tooling is generally movable at the geometry station between a lower and an upper position. In its upper position, the locators engage the receptors in the automotive underbody components and slightly elevate the automotive body components upwardly from the skid to the geometry position. Since the position of the tooling locators is fixed relative to the receptors, the tooling accurately positions the automotive body components relative to each other at the geometry position. With the automotive body components accurately positioned relative to each other, the body components are secured together by any conventional means, such as welding, clinching, or the like.
One disadvantage of these previously known lifter for automotive Body in White geometry systems is that the cycle time for elevating the automotive body components above the skid and to the final geometry position by the machine tools is rather prolonged thus increasing the overall cycle time of the automotive production line. This protracted time to first engage the underbody tooling, then to elevate the automotive body components to the geometry position in contact with upper tooling, since the tooling used to elevate the body components to the assembly position must undergo a double acceleration/deceleration cycle.
More specifically, with the skid positioned at the geometry station, the underbody tooling is first accelerated from a position largely beneath the skid and towards the automotive body components to deeply engage tooling into underbody cavities. In order to prevent damage to the automotive body components which would otherwise be caused by a rapid impact of the tooling against the body components, the tooling must be decelerated prior to contacting the body components so that only a xe2x80x9csoftxe2x80x9d impact occurs between the tooling and the body components.
Following the soft impact of the tooling against the body components, the tooling is again reaccelerated thus elevating the body components up to the contact of the upper tooling, creating at the end of the stroke a slight clearance between the body and skid.
Such acceleration, deceleration, reacceleration and final deceleration of the tooling, even if performed by a CAME system or an epicycloidal gear box, appreciably increases the overall cycle time for the framing system. This is particularly true, since the underbody tooling together with its movable support frame typically weighs several thousand pounds.
The present invention provides a xe2x80x9csoft touchxe2x80x9d lifter for an automotive Body in White geometry station which overcomes all of the above-mentioned disadvantages of the previously known devices.
In brief, as in the previously known devices, the automotive body components are supported by a skid prior to welding of the body components together. The skid itself is conveyed by any conventional conveyor system, such as a roller conveyor system, such that the skid together with its supported body components are introduced in a geometry station having a stationary base.
A pair of lift frames is vertically slidably mounted to the base at the geometry station so that the lift frame is movable between a first position and a second position. At its first position, the lift frame is largely positioned beneath the skid at the assembly station while, conversely, in its second position, the lift frame is moved to an elevated position relative to its first position.
Conventional underbody tooling is secured to the lift frame so that the underbody tooling moves in unison with the lift frame. Such tooling typically includes a plurality of locators which register with receptors, typically locating holes formed in the body components. Thus, as the locators engage their corresponding receptors and elevate the body components toward the upper tooling, and slightly away from the skid, the set of tooling precisely locates the body components relative to each other. The body components are then secured together in any conventional fashion, such as by welding.
Unlike the previously known lifters for geometry stations like framing systems, however, the lifter system of the present invention includes a pair of lift arms with one lift arm being vertically slidably mounted to the base frame at each end of the lift frame. These lift arms are thus movable between a lower position and an upper position. Furthermore, the lift arms register with the skid so that, as the lift arms are moved from their lower and to their upper position, the lift arms engage and elevate the skid together with the body components supported on the skid.
In the preferred embodiment of the invention, an elongated belt drivingly connects each lift arm with the lift frame. These elongated belts ensure that the lift arms move in synchronism with the lift frame. Just as importantly, however, is that the elongated belts move the lift arms from their lower and to their upper position at a speed one-half the speed of movement of the lift frame from its first and to its second position. Furthermore, as the lift frame approaches its second position and the lift arms simultaneously approach their upper position, the underbody tooling finally engages the automotive underbody and slightly elevates the automotive body components up from the skid at the very end of the upward stroke or upward movement of the lift arm and the lift frame.
Since the lift arms simultaneously move the skid in an upward direction prior to impact of the underbody tooling upon the automotive body components at the end of the stroke, the speed of impact of the tooling against the automotive body components is effectively reduced by the upward speed of the lift arms and thus of the skid. Consequently, unlike the previously known framing systems, the present system eliminates the need to decelerate the tooling in the middle of its stroke prior to impact against the automotive body components.